The present invention relates to a method for producing molded bodies from a base substance wherein the base substance for producing a molding solution is mixed with a solvent and subsequently this solvent is at least partly removed from the mixture and the molding solution is fed to a means for molding, and also to a device therefor.
In the present case, the term “molded bodies” subsumes all possible bodies obtainable from a natural or artificial base substance. This is generally accomplished with the aid of a molding tool whereby the base substance is brought into a mold for the molded bodies. An example which may be mentioned, purely for illustration and in no way exhaustive, is viscose fiber.
Viscose fibers are fibers consisting of cellulose as base material and industrially produced via the viscose process. The chemical nature of viscose fibers resembles that of cotton fibers.
Modal fibers are a similar product to viscose fibers. They likewise consist 100% of cellulose and, just like viscose fibers, are produced from natural pulp. However, a somewhat different process results in higher fiber strength and improved fiber properties being achieved.
The class of cellulosic fibers further includes Tencel and lyocell fibers. In the case of lyocell fibers, the nontoxic solvent NMMO (N-methylmorpholine N-oxide) is used to dissolve the pulp directly, without prior reaction with caustic soda and derivatization to the xanthate. Lyocell fibers are spun in a dilute aqueous NMMO bath by going below the solubility limit of the cellulose and thereby forming a thread. For this purpose, the corresponding spinning solution is pressed through spinneret dies. This lyocell process is described for example in DE 1 713 486, U.S. Pat. No. 3,447,939 or GB 8 216 566. The suitable spinning solution is produced for example in a horizontal kneading reactor as shown in DE 198 37 210 or WO02/20885 A1.
In these devices and according to the known methods, the spinning solution is produced in the further processable viscosity necessary for the spinning process and the associated cellulose concentration. However, the corresponding means for spinning can only process a spinning solution having low viscosity, but this significantly reduces the effectivity of the process for producing the spinning solution. Specific applications require very low viscosities and hence low cellulose contents, and this spinning solution can no longer be effectively produced using the known technology.
It is an object of the present invention to significantly improve the effectivity of the molding solution production and the production of the molded bodies.